TF Aluminum +12 Mag Extension for Glocks

I got this for my G34 Gen 5. The only issue I have is that it's closer to a +10 extension than a +12; if I try to fit more than 27 rounds (I attached it to a factory 17-rounder), the follower and extension spring will actually jam in the bottom of the magazine, and that's not fun to deal with at the range; getting the rounds and follower unstuck has resulted in the latter launching out and ending up downrange, thankfully close enough that the RSO could retrieve it without calling a cease fire). So rather than holding 29 rounds as advertised, it holds 27+1. I don't know if I just have a bad spring, but other than holding 2 less rounds than advertised (which I can live with) I like it. It sticks out a little less than a 33-rounder, making it a good middle between that and a 24-round mag.